From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4A87DC2BA17 for ; Mon, 6 Apr 2020 17:19:37 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8FBF1206F5 for ; Mon, 6 Apr 2020 17:19:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8FBF1206F5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 48wy2Y2nqFzDrNm for ; Tue, 7 Apr 2020 03:19:33 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=lst.de (client-ip=213.95.11.211; helo=verein.lst.de; envelope-from=hch@lst.de; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=lst.de Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 48wxzv1g57zDqyv for ; Tue, 7 Apr 2020 03:17:12 +1000 (AEST) Received: by verein.lst.de (Postfix, from userid 2407) id 0319068BEB; Mon, 6 Apr 2020 19:17:06 +0200 (CEST) Date: Mon, 6 Apr 2020 19:17:06 +0200 From: Christoph Hellwig To: Alexey Kardashevskiy Subject: Re: [PATCH 1/2] dma-mapping: add a dma_ops_bypass flag to struct device Message-ID: <20200406171706.GA3231@lst.de> References: <87sghz2ibh.fsf@linux.ibm.com> <20200323172256.GB31269@lst.de> <20200324075402.GJ23447@lst.de> <41975da3-3a4a-fc3c-2b90-8d607cf220e6@ozlabs.ru> <20200325083740.GC21605@lst.de> <213b0c7d-f908-b4f4-466d-6240c3622cd6@ozlabs.ru> <20200406115016.GA10941@lst.de> <348046e7-7a38-62d6-4df0-e4a537b98926@ozlabs.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <348046e7-7a38-62d6-4df0-e4a537b98926@ozlabs.ru> User-Agent: Mutt/1.5.17 (2007-11-01) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Greg Kroah-Hartman , Joerg Roedel , Robin Murphy , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, "Aneesh Kumar K.V" , linuxppc-dev@lists.ozlabs.org, Christoph Hellwig , Lu Baolu Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Mon, Apr 06, 2020 at 11:25:09PM +1000, Alexey Kardashevskiy wrote: > >> Do you see any serious problem with this approach? Thanks! > > > > Do you have a link to the whole branch? The github UI is unfortunately > > unusable for that (or I'm missing something). > > The UI shows the branch but since I rebased and forcepushed it, it does > not. Here is the current one with: > > https://github.com/aik/linux/commits/dma-bypass.3 Ok, so we use the core bypass without persistent memory, and then have another bypass mode on top. Not great, but I can't think of anything better. Note that your checks for the map_sg case aren't very efficient - for one it would make sense to calculate the limit only once, but also it would make sense to reuse the calculted diecect mapping addresses instead of doing another pass later on in the dma-direct code.